black substance from HCl???

[Anonymous]

Hello all, I'm new to refining but I'm completely interested. Recently, i bought a bit of zinc alloy 24K gold plated scrap jewelry. What i did so far was expose the zinc with a file, saving the filings of gold, and just plopped the jewelry in a bit of muriatic acid. I took chemistry for a year and i know that HCl dissolves zinc and not gold, so in my mind, i would have only gold. I left it in the solution for about an hour, and i started to notice a black powder forming along the gold.... i tried researching this and i couldn't come up with anything. does anybody know what this is? Help would be greatly appreciated. Thanks a lot

 

[jimdoc]

Maybe antimony?

 

[Anonymous]

isn't antimony have something to do with tin? there is only zinc and gold. If i'm wrong about antimony please let me know, obviously i'm new at this but it's so cool and fun i want to know more. Thanks

 

[qst42know]

There are dozens of zinc casting alloys. Many will contain significant quantities of aluminum and a host of other metal additives to improve it's physical properties and reduce porosity, etc..